Along with the widespread use of information and communication technology (ICT) systems, there has recently been widely used a disk array device using multiple storage devices (hereinafter collectively referred to as “disks”) typified by hard disk drives (HDD). Such a disk array device generally uses redundant arrays of inexpensive disks (RAID) technology to secure the safety of data by redundantly recording the data in two or more disks.
Here, the RAID is a technology to manage multiple disks in combination as one virtual disk (RAID group). There are seven levels of RAID, RAID0 to RAID6, depending on data arrangement and redundancy on each disk.
A RAID device protects data from trouble with a disk included in the RAID by inserting parity data into a stripe across the multiple disks included in the RAID. The RAID configuration is assigned with a logical unit number (LUN), and thereby is perceived as a disk region and used by a server.
In a disk array device having redundant data, when a disk breaks down, data stored in the broken disk is rebuilt and stored in an alternative disk such as a backup disk. Such processing is generally called rebuilding. By executing rebuilding, data redundancy is recovered.
Such technologies have been described, for example, in Japanese Laid-open Patent Publications Nos. 10-293658 and 2005-78430.
However, in the case where such a conventional disk array device includes two or more LUNs on the RAID, for example, even if restoration of any of the LUNs is completed by the rebuilding, another disk failure within the RAID causes all the data in the RAID to be lost. As a result, the data in the restored LUN is also lost.
Also, when there are two or more LUNs on the RAID device, even the restored LUN operates under the influence of performance degradation due to the rebuilding until the complete rebuilding is finished.